I think Ukrainian vs Russian in Ukraine, is like Gaelic vs English in Ireland.
Sure, nationalistic types will proclaim publicly preferring to speak Ukrainian over Russian, but privately, they probably do speak much more in Russian than Ukrainian.
Gaelic at least is a distinct language. Ukrainian and Russian use the same alphabet and similar etymologies and grammars. It’s like an older form of Russian, I think, like English with all the “thee”s and “thou”s still in it. Not claiming to be an expert.